I've been watching your post. I've not said anything because I haven't had a good answer for you. I can now add that the 1400/1430 will definitely print sizes other than 8.5 x 11, so as you assumed, your situation is not right. I only saw an event similar to yours once. In that rare instance, I got a partial print in the middle of a larger sheet. Rebooting the computer and starting over solved the problem, which I think was some kind of a buffer error.
From your post, it looks like you have tried all the obvious solutions. My only other ideas would be to reload your printer drivers (and be sure they are current) and, are you printing out of Lr? Early on, I found Lr printer setup very confusing and I made bunch of operator-error mistakes. If you are printing out of Lr, we may want to explore this further.